Railroad train monitoring system

ABSTRACT

Railcar monitoring utilizes instrumented, flexible pads supported within the truck pedestal jaws on the bearing adapters. The pads contain sensors for monitoring temperature pressure, shifting loads, truck hunting and the like and have circuitry for processing information received from the sensors and for processing and reporting departures of performance variables to a remote source. The system cyclically activates polling each pad on a car and communicates signals of critical departures and car identity to a remote source.

FIELD OF THE INVENTION

This invention relates to a monitoring system for railroad trains andthe like, and more particularly a system that uses an instrumentedroller bearing adapter pad to detect the occurrence and cause of poorperformance at wheel set, truck, freight car or train level.

BACKGROUND OF THE INVENTION

More than ever, railcar owners and operators need a better understandingof how their assets are performing. With heavier cars in service, thereis a greater need to identify “bad actors” (cars which can damage trackinfrastructure and lead to derailments) as soon as their performancebecomes unacceptable. There is also a need to increase average trainspeed by improving high speed performance and reducing unplanned serviceinterruptions through mechanical failures. Car owners increasingly seekto implement preventative maintenance programs to avoid mechanicalfailures and schedule repairs at a facility and time of their choice.Finally, with more automation of rail operations and increasingregulation to improve safety, the railroad industry needs new ways tomonitor the performance of trains, cars and railcar trucks.

Some of the performance criteria that need to be monitored includeroller bearing condition and temperature, roller bearing adapterdisplacement, wheel condition, truck hunting/warp/binding, brake statusand performance, whether a partial derailment has occurred andpotentially problematic track condition. Since some of these performanceproblems could lead very quickly to a catastrophic failure of the train,it is desirable to monitor and report exceptions to the locomotive or toa central data handling facility as quickly as possible. Further, giventhe demanding environment in which railroad trains operate, any systemmust be rugged, reliable and able to operate for long periods withlittle or no maintenance. In addition, to be cost effective, it shouldnot add significant cost to install and maintain the system. Since thereare more than 1.5 million freight cars in North America alone, and asystem of monitoring all cars in use is highly desirable, any suchsystem need to be able to deal with a very large address a very largenumber of potential devices.

One approach widely adopted in North America is to use wayside defectdetectors at fixed locations throughout the railroad network. Detectorsmeasuring bearing temperature (hotbox detectors) are common, while otherwayside detectors to measure wheel impacts, bearing condition (fromacoustical signatures) and lateral forces are gradually beingintroduced. However, while one detector can monitor many freight cars asthey pass, they can only provide a spot check on performance. It isquite possible that defects will only become apparent and escalate to acritical level between detectors. A system which is continuouslymonitoring railcar performance is needed.

Another approach to railcar performance monitoring has been to useon-board instrumentation. One such prominent system has been developedfor the Federal Railroad Administration. In this and other similarsystems, a number of instruments on different areas of a freight car areused to make discrete measurements before being communicated to acentral hub on the freight car. While providing a superior solution tothat provided by wayside monitors, wiring, complexity and costs increasethe investment required to monitor the cars.

SUMMARY AND OBJECTS OF THE INVENTION

This invention has the objective of providing means for continuously,while in service, monitoring the behavior and condition of the trucks,wheels and bearings of a railroad car and provide both regular assuranceof proper performance and, as necessary, warning of impending or actualfailure in a timely and useful manner to the operators and owners of thetrain whereof if forms a part.

It is a further objective of this invention that the performance of therailcar and its components could be combined with operating data fromthe locomotive to provide a complete train monitoring system.

It is a further objective of this invention to provide suchfunctionality with minimal recourse to making wired electricalconnections either between components mounted on the trucks of therailcar or between components mounted on the trucks and componentsmounted on other parts of the car and other parts of the train,including the locomotive.

It is a further objective of this invention that the components can beinserted or removed for inspection and repair or replaced during normalmaintenance work on the railcars.

It is a further objective of this invention to provide means for thetimely analysis of measurements made during operation of the train sothat the information about performance or failure can be sent in aconcise manner so that there is no need for detailed measurements to betransmitted.

It is a further objective of this invention that the messages sent aboutperformance or failure contain sufficient information that the exactlocation on the train of the item or items in question can beunequivocally determined, and that the location of the train, or indeedof the freight car can be reported, should that information beavailable.

It is a further objective of the invention that when operatingwirelessly, it can be expanded to exploit the available choices ofoperating frequencies (channels) to give relief from interferencebetween the successive (adjacent) cars in a train or from otherequipment operating in the same band of frequencies.

While the discussion which follows describes the vehicle as a freightcar, it will be understood that the same methods are applicable to anyrailroad or, in some instances, other multi-axle vehicles. Furthermore,while the description which follows features a freight car with twotrucks (or bogies), it is applicable to almost any configuration withmore or less trucks or axles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 are schematic views showing the arrangement of componentssuited for use in carrying out the objectives of the present invention;

FIG. 4 is an exploded perspective view of portions of a railcar truckillustrating the position of an instrumented pad of the invention withrespect to the railcar truck; and

FIGS. 5-7 are schematic views illustrating alternative configurations ofelements of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Turning now to FIGS. 1, 2 and 4, trucks 1, shown diagrammatically, eachcarry two axles 2 each with two wheels 3. The axle bearings 2 a andbearing adapters 4, best shown in FIG. 4, are configured so that eachbearing transmits the load which it carries and heat that it maygenerate through pads 16 and to the truck.

FIG. 4 illustrates a portion of a railcar truck 1 showing therelationship of an instrumented pad 16 relative to other truck parts. InFIG. 4, one end of a truck side frame 12 is shown. Each side frame has apair of downwardly extending pedestal jaws 13. Parallel side walls 14 ofeach pedestal jaw along with a roof section 15 combine to form apedestal jaw opening.

The truck also includes bearing adapters 4, one of which is shown inFIG. 4. The adapters have a generally rectangular upper surface withdepending legs extending from the corners of the top structure. The legshave facing curved side surfaces which are configured so as to rest onthe outer surface of a bearing 2 a mounted on the end of wheel bearingaxle 2. The adapter is typically comprised of cast steel. Adapter pad 16is generally rectangular in plan view and has depending legs. Theadapter pad 16 is preferably comprised of a cast or injected moldedelastomeric polymer. The adapter pad 16 is formed to seat upon the uppersurface of adapter 4 which, as indicated above, seats in turn on thebearing. The adapter and details of the pad as they relate to itsfunction as a load bearing and attenuation means are more particularlydescribed in U.S. Published Application No. 2005/0268813, dated Dec. 8,2005.

Referring further to FIG. 2, the pads 4 are seated on the upperrectangular surface of the bearing adapter. Each bearing transmits theloads which it carries and heat that it may generate through the adapterto the pad it carries and, thus, to the railcar truck.

FIG. 3 shows, in schematic form, an adapter pad 16 modified to carry outthe objectives of the present invention. The pad contains a plurality ofsensors 5 which are preferably embedded into its upper, side and lowersurfaces or into other locations such as its end surfaces as may benecessary for the purposes of the invention as explained more fullybelow. In preferred form, the pad 16 has an extended attachment portion17 located so as to be relatively isolated from the forces transmittedthrough the adapter 16. The extended portion 17 contains a power source18, an analog/signal conditioning means and analog to digital conversionmeans and an associated microprocessor unit 19 and a communications unit20 which is preferably a low power radio transmitter/receiver having anantenna 21. The sensors are electrically connected to the analog todigital conversion circuit unit and the microprocessor unit which, inturn, is connected to and controls the communications unit by means ofwhich messages can be sent and received. Various means of supplyingpower to the pad may be employed. The source of power may be a batterydelivering sufficient voltage and having sufficient energy storagecapacity so that when turned on periodically and briefly, as describedhereinafter, the pad can be functional for several years, consistentwith the normal service life of the bearing components used in thetrucks.

Alternatively, the power source may consist of an energy scavengingdevice which supplies energy to a rechargeable battery or capacitor. Astrain generated electrical power source may be employed. Although theenergy source may be a source mounted on the car body, it is preferredthat it be on the truck and most preferably on the extension to the padso as to avoid the need for electric wiring between relatively movablecar parts.

FIGS. 1-3 further illustrate a railroad freight car 22 having trucks 1with pads 16 with their associated sensors and control and communicationcircuit units 19 and 20. In the example described, each truck carriesfour pads 16 (one for each bearing) each having a power source 18,control circuit unit 19 and a communications unit 20, preferablycomprising a radio transmitter/receiver.

Mounted on the railcar body, preferably at a point at about midwaybetween the two railcar trucks is a data control unit 23 also having aradio/receiver which has the ability to communicate with the radios onthe pads 4 on its own railcar together with a microprocessor whosefunctions will be described hereinafter. The data control unit 23 islinked by cable 23 a to a communications device 24 shown herein as beingon top of the railcar, although other positions may be appropriate,depending on factors such as the type of car to which the invention isapplied. Under some circumstances and for some car types, the datacontrol unit and the communications device may be contiguous.

The communications device 24 is advantageously powered by a solar cellrepresented by reference character 24 a or other electrical means havingthe capability of maintaining continuous functionality. Communicationsdevice 24 serves to link the railcar either directly to the locomotivedrawing the train so that the engineer or other crew personnel haveimmediate notice of problem cars. Optionally, communication may be viatrack side automatic equipment identification means or to a cellular orsatellite radio system or other communication equipment to monitoringstations as desired by the user. In the event that wired communicationfrom the locomotive is available throughout the train as, for example,if electronic braking becomes standard, then the communications devicemay be connected to this communication line. The power supply for thecommunications device 24 may also provide power for the data controlunit 23 a, in which case the electrical connection 23 may be amulti-connector link.

Also shown in FIG. 1 is a hand-held unit 23 b containing amicroprocessor and the radio for communication with the instrumented pad16 by its radio and also with the data control unit 23. Unit 23 b,hereinafter called a “registrar”, is designed with very limited signaltransmission capability so that it must be placed physically close tothe pads 16 or the data communications unit 23 for communication to takeplace. This insures that the operator will communicate with only onesuch device without similar devices on other cars on the same or anearby train receiving the radio transmissions.

Although the use of a radio for making the communication by theregistrar is preferred, direct electrical contact could be employed.However, because of the harsh environmental conditions to which railcarsare exposed, direct electrical contact would be liable to reducereliability and would be more time consuming to carry out, especiallywhen communication with a large number of cars is necessary. The use ofthe registrar in carrying out the functions of the invention will bedescribed further below.

At this point, it should be noted that a feature of the invention is tofacilitate ascertaining the address for radio communication at the timeof installation of a pad or during replacement of a pad or a datacontrol unit. For this purpose, as an alternative to radiocommunication, a radio frequency identification (RFID) tag or acorresponding bar code or other readable version of the extended addresswhich can be read out and recorded by the registrar could be employed.

While the antennae shown in FIGS. 1 and 3 are schematically illustratedas of wire or rod form. In practice, they may be micro-strips orconformal arrays and may be, for example, metallic conductors on aceramic substrate.

Likewise, in place of battery power for the instrumented pads an onboardelectrical supply may be available in the railcar and could be employedif available. Alternative energy scavenging devices which derive energyfrom the rotation of the wheels could be used to generate electricalpower. As a practical matter in choosing a source of power, highpriority should be given to a power supply most likely to function forseveral years without the need for battery replacement or the need toperform other maintenance work.

As noted above, it is a feature of the invention that the radios withinthe pads 16 and the data control units 23 need only communicate over avery short range. For this purpose, radios conforming to theIEEE802.15.4 standard for wireless sensor networks are preferable. Thisis the short range standard of which the ZigBee sensor network systemsis exemplary. The power levels are low and range is limited but all thatis required is generally the ability to communicate between the pads onthe trucks of a particular car and the data control units of that car orwith a registrar held by a workman standing close by the car. Theexistence of standards for the data formats and open source software forusing these systems with capable micro-controllers makes this apreferable option. An especially compelling advantage to radiotransmission is that wiring on the trucks and wiring from trucks torailcar is undesirable as being susceptible to breakage, and wiringalong the length of a freight train very unlikely to be acceptableunless industry wide adoption of electronic brakes or the like isuniversally adopted.

Means for wireless communication based on the IEEE standard areavailable and adaptable to allow the instrumented pads and data controlunits to establish a network of connections without externalintervention. They can be set up to recognize the relationship of truckand axle location on a railcar or set up so that the digitalcommunication unit is informed of the configuration providing thereby amulti-hop means of linking the network together. Radios used in carryingout the above aspects of the invention are intended to be operatedintermittently at low power. Several frequency bands are acceptable invarious parts of the world. A suitable available frequency at which theradios will be operating in North America is about 2.4 GHz. Although itis preferably expected that the format and coding of messages willconform to the aforementioned IEEE standard, other arrangements arefeasible.

In an exemplary system, the instrumented pads 4 contain several sensorsfor measurement of dynamic and static vertical loads and shear orlateral forces imposed by the railcar truck and hence by the freight carby the bearing adapters. Conversely, these are the forces which theaxles, themselves attached rigidly to the wheels, and subject to trackirregularities, are applying to the truck. The exemplary instrumentedpads 16 also carry temperature sensors to give an indication of thetemperature of the associated bearing, since it is important for safetythat a bearing does not become overheated.

With reference again to FIGS. 1-3, in operation, the microprocessor onan instrumented pad 16 is normally in a passive, low power state, but isprogrammed to switch on briefly, periodically. It gathers readings fromeach of the sensors and performs preliminary analysis of the readings.The rational for the choice of sampling frequencies and the selection ofsensors to be read is based on the type of behavior being monitored andthe particular application. Sampling should be at a frequency severaltimes the highest frequency to be detected from the data. More frequentsampling will gain no further intelligence but increase powerconsumption.

The periodicities of sampling and of reporting are controlled by thedata control unit 23. Nevertheless, should the pads detect indicationsof fault or impending failure, the microprocessor on the pad may beprogrammed to switch on the radio which it controls and send anappropriate message via the radio to the data control unit 23. Anexample of such an event could be a sudden increase in temperature. Alarge voltage spike generated by the power scavenging device may also beused to activate the pads microprocessor if it were then in a low powerstate. In the absence of such a problem, the pad microprocessor followsits given schedule which would normally result in its being in a lowpowered state most of the time.

The data control unit 23 is intended to serve several purposes. Itcoordinates the timing of the cyclic testing performed by theinstrumented pad microprocessor and the timing of the messages issuingtherefrom. As an aggregator of information, it is programmed to compareinformation from all of the trucks on the railcar and draws inferencesfrom them as to the status of the car, for example, the data controlunit uses inference engine techniques to identify unsatisfactorybehavior such as swaying, bouncing or even partial derailment. It passeson information from the communications device 24. For example, thecommunications device 24 may include a means of measurement such as aglobal positioning system to provide information about vehicle speedwhich is useful in checking truck behavior such as hunting. Thisinformation may also be used to inhibit sensor checks when no purpose isthereby to be served in order to preserve energy usage.

Likewise, if desired, detectors of factors such as ambient temperatureand humidity (rain, snow and icing) can be built into the communicationdevice 24 or the data control unit 23 in the distributed inferenceengine functions for use described below. Additionally, the data controlunits 23 or the communications device 24 may contain a triaxialaccelerometer or rate gyro for triggering certain analysis modes orverifying readings made by the pad and providing information on avariety of car body motions.

As a conduit, the data control unit 23 passes messages on to thecommunications device 24 for onward transmission to the locomotive or toother remote receivers and receives, in turn, for the purpose of its ownanalysis and distribution to the pads, when appropriate, information orinstruction as, for example, from the locomotive or from other remotesources.

Alternative configurations for the monitoring system described in FIGS.1-3 are illustrated in FIGS. 5-7. In the embodiment shown in FIG. 5,each instrumented pad 16 has its own microprocessor and radio. Thisarrangement is intended to use a protocol for networking which allowsthe messages to be passed between pads on their way to and from thedigital communications unit 23.

In the embodiment of FIG. 6, all of the pads 16 from one truckcommunicate with a single microprocessor and radio unit 24 passing alongmulti-core cables 27. This minimizes the number of electronic componentsat the cost of making a large number of wire connections on the truck.The computational services performed in the microprocessor unit on thetruck may be somewhat different from those in the microprocessor unit ofFIG. 5. In this embodiment, all the analog to digital conversionfunctions are performed in the microprocessor and any inferencefunctions performed there make assessments for all sensors for all padson the truck.

A further alternative embodiment is shown in FIG. 7. In FIG. 7, eachinstrumented pad 16 has its own analog to digital conversion unit whichmay be incorporated into a microprocessor 28 on the particular pad.Those microprocessors can then communicate with the single data handlingunit 25 on the truck and hence to the data control unit 23. As in theconfiguration of FIG. 6, any inferences or data analysis performed atunit 25 takes account of information from all the sensors on all thepads on the truck.

Other options include standard CANBus communication schemes where wiredlinks are used. In addition, CANBus or other standards may beimplemented in the event of wide scale implementation of electronicallycontrolled pneumatic brakes potentially providing other options forcommunication schemes.

Communications along the train may be provided in a variety of ways. TheWiFi (IEEE802.15.11 standard) may be appropriate for very long freighttrains. For communication along passenger trains, Rail Transit VehicleInterface Standard, IEEE1473-199 would be applicable.

Furthermore, it should be noted that, in principle, it would be feasibleto let the instrumented pads communicate along the train, passingmessages from one freight car to the next. However, for long trains,this causes a message to make many hops which is essentially lessreliable than a single, more powerful link from each car to thelocomotive or other remote location. Other problems include thelikelihood that trains will be reconfigured with freight cars possiblybeing removed or shuffled or the train being pulled by a locomotive atits opposite end. Any such network depending upon pad-to-pad links fromcar-to-car would require reconfiguration of the train in marshallingyards.

As indicated above, it is a feature of the invention to have appropriatemeans of addressing and identifying each and every instrumented pad inrailcars used in the system. Further, it is necessary that theinstrumented pads on trucks on adjacent freight cars, be they on thesame train or not, continue to function while within each other's radiorange without mutual interference. It must be possible to form trainsfrom any freight cars and to replace a single pad on a truck withouthaving to replace all the other pads on the truck or the freight car.Even if there are no problems to report, it is important that the systemprovide assurance that it is still functioning properly. The preferredsystem described herein uses messages initiated by the instrumented padsfor this purpose. The alternative of using polling by the data controlunits to check the status of the instrumented pads requires the pads toswitch on and act as receivers at accurately controlled times and forperiods which require longer operation at full power than if they areallowed to send messages based on their own timing with the requirementthat the data control units is always in a receiving mode.

The instrumented pads which are to be mutually interoperable with thecorresponding data control units must all use matching frequencies. Theaforementioned IEEE802.15.4 standard designates frequencies or channelsin each frequency band. For example, in the ISM band, at 2.4 GHz thereare 26 channels. There is also a standard for the pattern of messagessuch that each form a packet of a multiplicity of 8-bit bytes of datawherein each byte has a preassigned meaning. Within this pattern, onebyte is assigned for a group number and two bytes are assigned for anaddress within a group. Another byte is assigned for the type of messagewhich might be interpreted as a command. The associated radio receiversand their controlling microprocessors are designed to ignore messagesreceived from a source in a different group. They do not detect messageson other frequencies then their chosen operating frequencies. However,they can change operating channels (frequency) under program control.They can act appropriately on messages that belong to their own group.For use on railroads, a larger number of devices than can be covered bythe two-byte address will be needed and, furthermore, means has to beprovided so that a data control unit can recognize messages frominstrumented pads on its own freight car. Instrumented pads have to beable to recognize messages from their own data control unit and bothhave to be able to tolerate potential interference from instrumentedpads and data control units on other nearby freight-cars either in thesame train or a passing train. They also have to be able to toleratepotential interference from other devices operating in the sameunlicensed band.

The identification number or address may be programmed into theelectronics module at manufacture.

The given address for an instrumented pad may additionally oralternatively be stored in an RFID (radio frequency identification) tagon or embedded into each pad 4. The physical placement of the pad on thetruck results in it being near to the trackside. Specifically, it couldbe on the outer side of the side frame of the truck and, thus, near toany trackside monitoring equipment. That provides the opportunity for atleast the recognition of passing devices by the fixed equipment and, ifactive RFID tag technology is used, to allow for an alternativecommunication route from car to central data repository or the owners.

The given address may conveniently be visible as a readable numberoptionally with a barcode for the convenience of users, though thedemanding operational environment may make this alternative of limiteduse.

It will be apparent that any addressing scheme which provides sufficientindividual addresses or identities may be used. The address of the padmay be made conforming to the extended Internet Protocol (IPv6)addressing scheme, using 6 bytes so that these devices can have theirown IP addresses.

The preferred embodiment described below can be augmented to usemultiple channels (radio frequencies) thereby providing a means ofvirtually eliminating interference between adjacent cars in a train.

The underlying purpose of the invention is to be able to monitor thebehavior of all the trucks and bearings and wheels on a train. An alarmmessage must get through from any railcar to the locomotive or to theremote data handling service as quickly as possible, preferably within afew seconds.

However, the burden of transmitting all the data that might be sampledin performing such monitoring is extremely large and, for the most part,detailed data is not significant. Preferably, only the observationswhich imply some fault or misbehavior are recognized. To reduce theradio traffic to manageable proportions, the system is designed toprocess the raw sensor data, looking for signs of trouble and then sendonly essential indicative information. To this end, a distributedinference engine is used, sharing the essential functions between themicroprocessors at the instrumented pads and at the data control unit23. It is a purpose of this invention to reduce the radio trafficbetween pads and data control unit so part of the data analysis is doneat the pads and only relevant information is transmitted to the datacontrol unit from the pads for further analysis and recognition offaults.

In the example system illustrated above, the microprocessors 19 at theinstrumented pads 16 take a series of measurements and treat them as atime series. The search algorithms, forming an inference engine, canidentify, for example, periodicities and cross correlations in andbetween time series so that any behavior detectable at pad level will beseen. For instance, hunting of a truck back and forth across the line ofthe rails, is at a frequency determined by truck geometry and wheelrotation speed. Swaying and rocking of the car is at frequenciesdominated by the mass spring systems of suspension and load. To variousextents, depending on vehicle design, these irregularities in behaviorwill be apparent in the changing load and distribution of load in theinstrumented pad, which can sense, for example, vertical and shear andbraking forces. Wheel irregularities create repetitive patterns offorces at the rotation frequency which can be calculated from vehiclespeed. Track defects can generate large and sudden forces in the wheels,bearings and truck and on to the car and its load.

If such behavior is inferred at the instrumented pad and the magnitudeis sufficient to cause alarm, relevant attributes and timing (relativeto the time of transmission of report) can be passed to the car's datacontrol unit.

Given that more than one instrumented pad may report misbehavior, thenthe components of the inference engine in the data control unit takeresponsibility for making assessments for the whole truck and ultimatelyfor the freight car. When serious trouble is inferred, then messages aresent via the communications link 23 a, 24 to the locomotive, etc.

Examples of performance that the system is capable of monitoringinclude:

Bearing temperature—A temperature sensor in instrumented pad 16 monitorsrelative changes in temperature against other bearings and provides analarm threshold or long term trends to link to bearing condition. Thewell-being of a roller bearing can be inferred using either trends oralarm levels, avoiding a potential bearing burn off and possiblederailment and providing a direct measurement that can be used to avoidfalse alarms from wayside hotbox detectors. As a further purpose of thisinvention, the observations from wayside detectors for temperature andother effects can be compared with those from the on-board system formutual calibration and verification purposes.

Bearing condition—Use a load sensor in the top of instrumented pad 16 tomonitor vibrations emitted from the bearing (transmitted through theroller bearing adapter). Specific bearing defects can be inferred fromfrequency spectrum analysis. Identifying a failing bearing in its earlystages is important in preventative maintenance programs.

Wheel condition—A load sensor in the instrumented pad to detect highamplitude loads (compared to the background) that repeat periodically(function of wheel diameter and speed) to identify a flat spot orshelled wheel tread. It may also be possible to identify hollow wornwheels using some of the other sensors in the instrumented pad.Monitoring wheel impacts may allow an owner to schedule a wheel changeout before it is identified by a trackside Wheel Impact Load Detectorresulting in unscheduled maintenance. It may also provide insight intocause of failure.

Wheel derailment—Using the same instrumentation as for the WheelCondition, but looking for a higher frequency and a similar signal fromboth wheels in the wheel set. Identifying when a wheel set has derailedprevents a possible full derailment and possible catastrophicconsequences.

Truck Hunting—Using load sensors mounted in the instrumented pad so asto detect longitudinal, lateral and yawing forces, monitor rapidlychanging loads (and hence the angle of attack of the wheel set)indicative of axle or truck hunting. By analyzing such loads monitoredfrom both wheel sets on a truck, and both trucks on a car, truck andaxle hunting as well as truck warp can be identified. Additionally byassessing the angle of attack of wheel sets on each truck, highrotational friction caused by binding side bearings or dry center bowlscan be identified. Identifying these conditions helps to prevent damageto freight car trucks and lading as well as to the track infrastructure.

Car weight—Sum the load measured in all eight instrumented pads on afreight car to determine its weight. Even a coarse measurement (say plusor minus 10% of full load) will provide useful information for thosecharged with assessing the performance of freight cars and theircomponents. A further benefit comes from detecting load imbalances dueto improper loading or shifting in transit.

Displaced roller bearing adapter—By monitoring the load in theinstrumented pad legs it is possible to identify when a roller bearingadapter has become displaced. This provides information about whatcaused the displacement as well as drawing attention to an urgentmaintenance need to avoid damage to the roller bearing.

Brake performance and status—Monitoring the longitudinal forces at aninstrumented pad provides information on the force being applied frombrake pads to wheels. This can provide insight into braking efficiency(excessively high brake loads indicating brakes may cause wheels tobind, excessively low brake loads indicating the brakes are not workingproperly. In addition, checking brake status can be used to send analarm if the train is moved with some of the handbrakes applied.

Track defects—Monitoring the vertical loads in the instrumented pads andcomparing these between wheel sets gives car owners insight into trackdefects that may cause damage to freight cars or their lading.

While several alternatives have been identified above for theconfiguration of the devices and for the communication between them thepreferred embodiment is described hereinafter.

It will be apparent to those familiar with the programming ofmicrocontrollers and the protocols and capabilities of both low powerand satellite or cell phone communications that the functions describedherein are feasible with existing technology and components. Forinstance, the Micaz low power motes, made by Crossbow Corp., of PaloAlto, Calif., with their built-in ChipCon radios can perform thefunctions of the Pads and of the data control unit. The communicationsdevice 24 is a model DS300-RDT made by Stellar-Sat, Inc. That device hassignificant computing power so that some of the functions ascribedherein to the data control unit 23 can be performed in the DS300-RDT.Indeed, the two devices may well be combined or their functions sharedso that the distinction could become unnecessary.

The power source consists of an energy scavenging device, such as apiezoelectric film from Measurement Specialties, Inc., of Hampton, Va.,together with a charge storage capacitor or a rechargeable battery.

The instrumented pads are programmed in manufacture with a group number,a channel number and a unique, extended address which is stored innon-volatile memory and matches the data in the RFID tag and barcode ifused. With appropriate programming, the number of available addressesfor distinct instrumented pads can be increased as much as necessary.

The group number serves, as is standard with such IEEE802.15.4 systems,to distinguish this application from any others which might use the sameradio frequency (channel).

As the pads are installed their extended addresses are read by registrar23 b which is equipped to gather the RFID or barcode data. The userinstructs the registrar, by means of its keypad and screen as to whichlocation on the truck and hence on the freight car is occupied by eachpad. The registrar is then placed in proximity to the data control unit23, and using the radio channel, passes the address and location datafor the pads on that data control unit's own freight car into the datacontrol unit.

To avoid the use of RFID or barcode means the registrar canalternatively exploit the functionality of the pad and electronics whichis programmed always to send out messages whenever it has poweravailable. Those messages, as are explained hereinafter, always containthe extended address of the pad, so that the registrar can gather itwhen it is close to the pad. This mode of operation has the disadvantageof requiring the pad to be electrically powered for the dialog to takeplace, which is not convenient if the pad is to be powered in normaloperation by energy scavenging means. If extra means are provided toprovide electrical energy, for example, by induction, then the use ofthe radio communication becomes preferable.

The registration of pad data could alternatively be conveyed into thedata control unit by other means, such as using the data link 24. In anycase, the data is recorded in the data control unit in non-volatilememory so that temporary loss of power does not obligate repeatregistration. The process of registration allows tracking of devicesthroughout the railroad system.

Once the pad identities are written in to the data control unit,subsequent transmissions from instrumented pads will be recognized bythe data control unit if they emanate from a registered instrumentedpad. Likewise subsequent transmissions from the data control unit can bedirected to the correct instrumented pads.

Irrelevant messages that are picked up from nearby instrumented pads anddata control units are not a problem if they do not collide in time withthe desired messages. They can simply be ignored. If they collide, thenmessages will be corrupted. However, by using the normal IEEE802.15.4standards for cyclic redundancy checking of message validity, they willnot be recognized and will, therefore, be missed. To minimize thisproblem, the data control unit manages the timing of messages to andfrom its own instrumented pads.

Initially, instrumented pads will start sending messages at the rate ofone a minute or similar rate, just after they are powered. This message,broadcast as if for any recipient, but with the correct group number andon the appropriate channel carries the pad's address as the senderaddress. This is the only type of message that is sent as a broadcast inthis scheme. The pad then waits briefly for a reply. The data controlunit, when powered, acts as a receiver so it picks up the message.Because it can recognize the sender address as belonging to one of thepads for which it is responsible, it replies immediately with a messagethat instructs the pad as to which data gathering task to perform andwhen (how much later) to report back. The pad is programmed so that anymessage it receives which uses its own full address is accepted ashaving come directly or indirectly from its controlling data controlunit and automatically sends replies back to that sender. As a result,the pads will need no further addressing instruction for the rest oftheir useful lives, since they will automatically take instruction fromand report back to whichever device addresses them directly and are nearenough. Having received a message from the data control unit, the padcan revert to low power (sleep mode) until it has to perform its nexttask.

This scheme allows pads to stop functioning due to loss of scavengedpower and still come back and be connected into their appropriate datacontrol unit when power is restored.

The scheme allows a data control unit to be replaced in the network bygiving it the addresses of the pads for which it is responsible. Asingle pad can be replaced in the network by giving its ID to theappropriate data control unit.

The scheme also allows other devices to be operated in the network, aslong as they have an associated, proximate data control unit.

By the time that all the instrumented pads belonging to a data controlunit have had a round of communication, they are on a schedule thatbrings them up in turn at times which the data control unit cananticipate. The instrumented pads are essentially incommunicado in theintervening period to save power.

The scheme for scheduling messages in the system deliberately keepsmessages from the instrumented pads on a single freight car separate intime, so radio signal collisions are avoided. Because the instrumentedpads themselves are only acting as receivers very briefly, the risk ofthem receiving spurious messages is also small. Because the scheduledradio transmissions from the instrumented pads are very short, e.g., afew milliseconds, compared to the intervening quiet period, the chancesof radio signal collisions from adjacent freight cars or othercompletely independent devices are also low. However, they willeventually occur. The standard approach for the IEEE scheme is that aradio about to send out a signal first goes into receiver mode to see ifany other is transmitting on the channel. If so, it delays sending by arandom amount of time related to message length. This procedureeliminates most collisions.

If an expected, scheduled message from an instrumented pad does notarrive within a reasonable time frame, then the data control unit cantake a number of different actions. It can sometimes detect that amessage was received but was corrupted. Knowing that the sendinginstrumented pad will be expecting a reply for a while, it can send amessage instructing a slight random shift in timing so that if theproblem comes from an adjacent freight car, then the next message willvery likely get through.

Correspondingly, the instrumented pad can repeat its message, out ofschedule, if it does not get a reply so that the data control unit,always powered and normally acting as a receiver, will soon pick up theconnection and can, as in the initial start-up process, assign a newschedule time for transmission. The data control unit can wait anothercycle to see if it was a chance event, it can quiet its otherinstrumented pads for a while when they call in, so that they do notinterfere with transmissions from the missing device. By these and othersimilar stratagems, the instrumented pads and data can take steps torestore communications. Eventually, if all these fail, the data controlunit will report loss of communication via the messaging link 23 a.

It is a feature of this invention that the pads never stop trying tomake contact with a data control unit so long as they have sufficientpower and no external message to a Pad is capable of stopping thatprocess although a long, but not indeterminate, delay before the nextreport is naturally allowed.

With communications established, the data control unit instructs thepads as to which data acquisition task to carry out and when to reportback so as to provide information to enable the inferences indicatedabove to be performed. Such tasks include but are not limited to:measure temperatures, take average forces, deliver spectral data onlateral or vertical or longitudinal forces, measure vertical forces overcycles at wheel rotation frequency. Each of these measurement sequencescorresponds to a particular inference that may be drawn if the datajustifies it.

For each task a time to wait before reporting back is assigned. For eachtask a time at which the measurement should be taken is assigned orperiodicity is assigned.

The tasks may require the pads to make intermediate measurements andstore them temporarily between radio reporting intervals. Theseintermediate, timed actions can be undertaken without intervention ofthe data control unit. Between such activities, the pads revert to lowpower sleep mode, provided there is sufficient time to restart, theprocess results in energy economy.

Every report sent back by a pad identifies the task that was requestedand the elapsed time since the data in the set was gathered.

Every report includes status information (status byte) on thefunctionality of the pad components especially the sensors.

The set of requests includes the option to request reporting receivedsignal strength as a check on communications.

The data control unit schedules the reporting times so that the radiotransmissions do not conflict with each other.

The data control unit can parameterize the data requests with relevantinformation such as ambient temperature or vehicle speed. The commands,which select the measurement task, can be made location dependent byusing the GPS information. The commands can be influenced by themeasured accelerations at the data control unit when such facilityexists.

The data control unit has a default program of measurements to runthrough, using its pads as data gatherers so that regular assessments offreight car behavior are made in a timely manner. However, this regularpattern can be superseded by commands sent to the data control unit fromthe central data repository or by command of the owners or operators.

The data control unit in its role as information aggregator merges thedata from the pads and makes adjustments as necessary for the slightlydifferent times at which the data was reported and gathered. The datacontrol unit then performs the assessments described above for theinference engine to check if the freight car, its trucks or wheels oraxles are behaving sufficiently poorly that a report to the central datahandling location or owner or operator or locomotive is needed. If so,then the report can be sent. It is important to minimize the data beingsent because the data transmission may be priced by quantity, and therecan be many rail cars sending data. Nevertheless, the data control unitwill schedule the sending of an “all's well” message at suitableintervals should nothing be amiss.

The rules for assessing freight car performance are designed to betolerant of missing data, since it will be apparent from the abovedescription of the system that either due to communications difficultiesor to the rigors of the environment, components may fail to provide allthe requested data.

Because this preferred embodiment delegates the initiation of datadialog to the pads, a further advantage is that should some extremecondition occur the pad can send an unsolicited report at any timebetween scheduled reporting intervals. To minimize data traffic, thesame approach is taken in the sending of data from the data control unitto the central data base.

For a version of the invention that can take advantage of the choice ofseveral (e.g., 26 in the 2.4 GHz band) available operating frequencies,the following additional features are added. The central data controlcan extract from GPS data sent by the cars, which pairs of cars areactually adjacent. If the cars are reporting communications problems,then one of such a pair can be told by communication, from the center tothe car, to switch to another channel. Networks of IEEE802.15.4 devicescan be programmed to do frequency hopping by mutual agreement to avoidinterference. In the event that communications are lost, such deviceswill broadcast messages on a sequence of difference frequencies until aresponse provides the basis for reestablishing communications. Limitingthe choice and predefining the sequence of frequencies to be triedexpedites the recovery process. The system can also be programmed toprovide deliberate changes of frequency by sending the instructionstherefor as part of the regular dialog between pads and data controlunit.

Thus, by the means described, the objectives of the invention arecarried out.

1. A monitoring system for monitoring performance criteria of a railcar, said railcar including a car body and a plurality of trucks each carrying one or more wheel sets mounted on said railcar, comprising: one or more pads disposed between each wheel set and its corresponding truck; one or more sensors disposed on said pads, said sensors measuring parameters relevant to the operating performance of the railcar; a computational element disposed on said pads programmed to control the periodicity and sampling frequency of readings from said one or more sensors and for performing an analysis of data gathered via said readings; a communication element disposed on said pads for transmitting data selected as a result of said analysis; and a data control unit, mounted on said railcar, for uniquely addressing each pad, for receiving data transmitted from said one or more pads, for analyzing said data, and for selectively communicating said data to a receiver located at a location remote from said railcar.
 2. The monitoring system of claim 1, wherein said receiver is located in a locomotive, in a train of which said railcar is a part.
 3. The monitoring system of claim 1, wherein said data control unit programs said computational element on each of said pads to control (i) the sampling frequency for each sensor associated with said pad; (ii) the periodicity of sampling for each sensor associated with said pad; and (iii) how often collected data should be transmitted via said communications element to said data control unit.
 4. The monitoring system of claim 1, wherein said data control unit communicates said data to said remotely located receiver wirelessly.
 5. The monitoring system of claim 1, wherein said communication element transmits said gathered data wirelessly to said data control unit.
 6. The monitoring system claim 1, wherein each of said sensors is responsive to one of a plurality of variables, including changes in compressive stress, shear stress and temperature within said pad.
 7. The monitoring system of claim 3, wherein said pad may transmit an unsolicited or unscheduled message if said computational element determines that said gathered data is outside an acceptable range for a particular sensed parameter.
 8. The monitoring system of claim 7, wherein said data control unit can draw inferences regarding the status of said railcar based on data gathered from all of said pads.
 9. The monitoring system of claim 1, wherein each of said pads is identified to said data control unit by a unique address.
 10. The monitoring system of claim 8, wherein said data control unit transmits a message to said remote receiver when it determines that said inferred status indicates a problem in the operation or performance of said railcar.
 11. The monitoring system of claim 1, wherein said data control unit periodically transmits a status message to said remotely located receiver when an inferred status indicates that said railcar is operating with acceptable boundaries.
 12. A system for monitoring performance of a railcar, wherein the railcar has plural trucks each having wheel sets spaced apart on axles and bearing assemblies individual to each wheel of a wheel set relatively rotatably mounted on the axles in association with each wheel, the trucks having side frames having spaced pedestal pockets within which the bearing assemblies are received, the combination comprising an elastomeric, load bearing pad located between a pedestal pocket and a bearing assembly, said pad allowing for limited relative movement between the bearing assembly and the pedestal pocket and providing damping of shock and abrasion, the pads further permitting controlled yaw movement of the axles within the pedestal pockets, the pads having at least one sensing device supported thereon, said at least one sensing device being a temperature sensor disposed on the pads adjacent a bearing for sensing bearing temperature, and control circuitry including a first communications circuit mounted on each pad for receiving signals indicative of temperature of the bearing unique to that pad and a second communications circuit mounted on a railcar body, said second communications circuit including logic circuitry for periodically addressing each sensing device on the railcar and for communicating values derived by said sensors to a remote location, said values being communicated only upon a determination by the logic circuitry that the values are indicative of a potential operating failure.
 13. A system according to claim 12, further including a power supply associated with each said pad.
 14. A system according to claim 13, where said power supply is a battery.
 15. A system according to claim 13, wherein the power supply is an energy scavenger device.
 16. A system according to claim 15, wherein the power supply derives energy from the rotation of the wheels of the railcar.
 17. A system according to claim 15, wherein the energy scavenging device is a vibration responsive device, converting vibrational energy of the railcar to electric power.
 18. A system according to claim 17, wherein the energy scavenging device is integrally mounted on the pad.
 19. A system according to claim 12, wherein the communications circuits comprise low power, wireless receiver/transmitters conforming to the low power radio standard of IEEE802.15.4.
 20. A system according to claim 12, further including a solar powered energy source for powering the second communications circuit.
 21. A system according to claim 12, wherein the pads have a second sensing device supported thereon, said second sensing device being a vibration sensing device and being positioned on the pad to sense bearing vibration, said first communications circuit receiving signals from said second sensing device representative of vibrations and identifying vibration levels indicative of potential failure and communicating said signals of vibration level indicative of potential failure to said remote location.
 22. A monitoring system for monitoring performance of railcars in a train including an operating locomotive wherein each railcar comprises a railcar body and supporting trucks with side frames having pedestal openings, wheel sets including an axle and spaced wheels retained by the pedestal openings, the axles carrying wheel bearings retained in said openings and elastomeric pads within each of the openings for attenuation of loads communicated between the bearings and the pedestal jaws, the pads being instrumented with sensing devices for sensing operating parameters selected from the group comprised of vibration, dynamic and static vertical loading, shear forces and temperature, each pad having an associated microprocessor, each microprocessor being programmed to a periodically active state to scan the sensed data for indications of potential failure, each pad further having a transmitter, the system further comprising a data gathering unit mounted on the railcar body including means for receiving signals indicating potential failure and transmitting said signals to a remote location.
 23. A monitoring system according to claim 22, further including a receiver located in the locomotive for communication of said signals to crew members located within the locomotive.
 24. A monitoring system according to claim 22, wherein the transmission of signals to the locomotive receiver is a wireless transmission.
 25. A monitoring system according to claim 24, wherein each data gathering unit broadcasts to the receiver in the locomotive, a signal identifying the railcar from which a signal indicating potential failure is being broadcast.
 26. A monitoring system according to claim 24, wherein the means for receiving and transmitting signals to the remote location is inactive in the absence of a signal indicative of potential failure.
 27. A monitoring system according to claim 22, further including a power supply for the microprocessors on the pads, wherein said power supply includes a switch, said switch being operable to switch on the power supply upon scanning of the sensors on the pad.
 28. A method of monitoring performance of wheeled, interconnected mobile units having bodies supported by wheels, wherein one of said mobile units is a controllable prime mover and the remainder of said mobile units are interconnected to the said one of said mobile units, said method comprising: providing interfacing pads between the wheels and the bodies of the wheeled mobile units, said pads having embedded sensors for measuring operational parameters of said wheeled mobile units, said pads being programmable to control the sampling frequency for each sensor and the periodicity of sampling for each of said sensors; and providing, on said pads, a computational capability for evaluating said measured operational parameters, and for identifying performance behavior derived from said measured operational parameters considered to be sufficient to cause alarm; and communicating to the prime mover messages identifying only the performance behavior sufficient to cause alarm.
 29. A method of monitoring according to claim 28, further including the step of including in the messages communicated to the prime mover an identification code unique to the mobile unit from which the signals identifying behavior considered to be sufficient to cause alarm originate.
 30. A method of monitoring a load bearing structure comprising the following steps: disposing a plurality of elastic, compressible pads between relatively rigid elements in the load bearing structure providing the pads with embedded sensors for sensing parameters selected from the group consisting of temperature, displacement, velocity, acceleration, stress, strain pressure, force and combinations thereof, a microprocessor for processing data received from said sensors and a low power transmitter/receiver and an energy scavenging and energy storage device periodically activated to power said microprocessor; programming the pads with an identifying address unique to each pad, said address including a number to distinguish the pad application from other applications using the same broadcasting frequency; locating a data control unit on the structure in proximity to the pads, said unit having receiver and transmitting abilities and a data processing unit with storage; programming the data processing unit with the unique address of each pad; programming the data processing unit to activate the power source for the pads in timed sequence; communicating to the pad contacted the task the pad is to perform and a time for reporting back; processing data signals received from a pad; merging information derived from other pads in communication with the data control unit; drawing inferences from the data received from the pads to determine whether alarm conditions exist; and communicating any such alarm condition to a location remote from the data control unit.
 31. A monitoring system for monitoring the behavior of a railcar, said railcar including a car body and a plurality of trucks each carrying one or more wheel sets mounted on said railcar, comprising: one or more pads disposed between each wheel set and its corresponding truck; one or more sensors disposed on said pads, said sensors measuring parameters relevant to the operating performance of the railcar; one or more first computational elements disposed on said one or more pads for gathering data from said one or more sensors; a second computational element, for receiving data from said one or more pads; and a logical inference engine distributed over said one or more first computational elements and said second computational element, said logical inference engine deriving inferences regarding the behavior of said railcar based upon all available data.
 32. The monitoring system of claim 31 wherein said logical inference engine uses information available from outside sources in additional to all data collected regarding said railcar in deriving said inferences regarding the behavior of said railcar.
 33. The monitoring system of claim 32 wherein said outside sources are selected from a group consisting of a GPS device, an ambient temperature sensor, a speed sensor, an ambient humidity sensor, an accelerometer and a gyroscope. 